Extension-ladder.



17?. A. DRUMMOND.

EXTENSIONELADDEB. 'urmourqr rum) APILH. 1911.

Patented Nov. 12,1912.

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Specification of Itetters Patent.

Patented Nov. 12,

Application filed April 2'1, 1911. Serial No. 623,664.

To all whom it may concern:

ill

Be it known that I, FRIEDRICH. A. DRUM MONK), a subject of the King of Great Britain I and Ireland, residing at London in the Province of Untario and Dominion of.

Canada, have invented certain new and use ful Improvements in Extension-Ladders, of

which the following is a specification, reference heing had therein to the accompanying drawings.

The invention relates to extension ladders and consistsfirst in the peculiar construc tion and arrangement of the dogs or holding devices for securing'the'ladders in diilerent positions of adjustment, and further in various features of construction as hereinafter set forth. Y

In the drawings,l igure l. is a sectional perspective view; and F 2 is a central longitudinal section.

A and B are respectively the lower and upper ladder sections which are arranged to engage each other in the usual way, the side rails of the upper section preferably fitting within the side rails of the lower section.

C is a strap at the upper end of the lower section for embracing the upper section and having centrally secured thereto, the sheave or pulley l).

E are straps secured to the lower end of the upper section embracing the opposite side rails of the lower section. straps C and E will together hold the lad der sections in' slidahle engagement with each other.

tine of the objects of the invention is to avoid all danger of accident and collapsing of the ladder through the breaking of a rung. it is usual to attach the holding dogs which secure the ladder sections, in different positions of adjustment. to the lower rung oft-he upper section, and thus it at anytime this rung is broken a serious accident may occur. llfith my improved construction the dogs so attached as to engage the lower ends of the side rails of the upper ladder sect-ion and. thus secure the same without depending; upon the strength of the rung.-

in detail, F and F are dogs which are mounted upon a cross rod G pivotally engaging hearings in the opposite side rails of the upper ladder section. These dogs are fashioned to overlie the outer face of each side rail and are then hent inward beneath the end oi? the rail and extend a suiticient Thus the.

distance to engage with the rung of the lower ladder section. The inclination of the bent portion F forms a cam which forces the upper section inward against the lower section. increasing the frictional engagement'and assisting in holding the parts from movement without transmitting all of the downward stress to the supporting rung.

For disengagingthe dogs, the cross rod G is provided with a rearwardl projecting hook or arm H to which one en of the rope or cable I is attached, said cable extending around the lower rung of the ladder section and then upward over the sheave or pulley D and then down again to the lower turn; of the upper ladder section. The arrangement is such that by pulling the rope I in one direc .tion the upper ladder section is hoisted, while by pulling in the opposite direction or by drawing upon a portion of the rope attached to the hook H the dogs will he thrown outward so as to clear the the lower ladder upper section to he lowered.

To increase the strength of the ladder I rungs of section and permit the! preferably employ reinforcing metallic rods which extend in a groove on the under face of each side rail. These reinforcing rods J near the ends oi the rails are bent and 6X- tend through bores in the rails to the ends thereof where they are provided with adjusting nuts it. These permit of tensioning the rods up so as to greatly increase their efficiency in trussing the rails.

it will he understood that a ladder con structed as described ha'sa large factor of safety and at the same time. is easily manipulated and is simple in construction.

What I claim as my invention is:

1. In an extension ladder, the comhina-' tion with a. lower section and an upper section slidahy engaging each other, of a locking dog pivotally attached to the upper section and extending beneath and 111 contact with the end of the side rail thereof said dog being adapted to engage the rung oi the lower ladder section and constructed to force the upper section inward against the lower.

2. ln an. extension ladder, the coniloinw tion with a lower section and an upper section slidahly engaging each other, of a locking means comprising across her pivotally engaging the side rails of the upper ladder section, dog-"members secured to said cross rod overlapping the fr hnt face of said side rails and extending beneath and in contact with the ends thereof, said dogs projecting inward for engagement with the rungs of the lower ladder section.

3. In an extension ladder the combination with a lower and an upper section slidably engaging each other, of a securing device therefor comprising a rod pivotally engaging the side rails of the upper ladder section, and dogs mounted upon said rod lying adjacent to the outer faces of said side rails and extending inward in an inclined position adjacent to the lower ends of said side rails and into engagement with the rungs of the lower ladder section.

4. In an extension ladder, the combination with a lower and an upper section slidably engaging each other, of a securing device therefor comprising a cross rod pivotally engaging the side rails of the upper ladder section, dogs mounted upon said cross bar and bent to lie adjacent to the outer face of said side rails and then to extend inward adj acent the lower ends thereof into engagement with the rungs of the lower ladder section, a hoisting cable for loop of said hoisting cable extending from the lower rung of the lower ladder section and operatively connected to said rod to rock said dogs out of engagement with the rungs.

5. In an extension ladder, the combinahion with a 'lower section and an upper 'rtionslidably engaging each other, of a. locking dog pivotally attached to one of the sections and having a cam face for engaging the rungs of the other section, said cam face being constructed to force the sections toward each other.

In testimony whereof I 'affix my signature in presence of two witnesses.

FREDRICK A. DRUMMOND.

Witnesses:

JAMES P. BARRY, WILLIAM Paonn.

extending the ladder sections, and a return 

